Geomembrane and method of manufacture

ABSTRACT

A geomembrane comprising a unitary structure fabricated by co-extrusion including a center core, a thermoplastic adhesive layer secured on one side of the center core, and a textured layer secured on the opposite side of the center core. The geomembrane is utilized in the manufacture of a liner for earthen constructions by employing the thermoplastic layer of the geomembrane to secure the geomembrane to a geosynthetic clay liner.

TECHNICAL FIELD

[0001] This invention relates generally to geomembranes of the typeutilized in the fabrication of liners for earthen constructions such aslandfills, canals, ponds, etc., and more particularly to an improvedgeomembrane comprising a unitary structure fabricated by co-extrusion.

BACKGROUND AND SUMMARY OF THE INVENTION

[0002] Ground water contamination is a primary environmental concern.One method of controlling ground water contamination comprises thelining of landfills, canals, ponds, and similar earthen constructionswith a liner comprising a geosynthetic clay liner and an underlyinggeomembrane. In this manner seepage from the lined construction into theunderlying ground water is prevented.

[0003] More particularly, liners for landfills, canals, ponds, andsimilar earthen constructions may comprise a layer of bentonite. Theupper surface of the bentonite layer is secured by a layer of wovenpolypropylene. A layer of non-woven polypropylene textile is positionedbelow the bentonite layer. A geomembrane is secured to the lower surfaceof the non-woven polypropylene textile which may be provided with atextured lower surface to prevent shifting of the liner relative to theunderlying construction.

[0004] Heretofore the fabrication of liners in which a geomembrane issecured beneath a geosynthetic clay liner has been complicated by thenecessity of applying a glue layer to the upper surface of thegeomembrane in order to secure the geomembrane to the geosynthetic clayliner. The application of the glue layer has required a separatemanufacturing step which has typically been carried out at a remotelocation. The cost of manufacturing the liner is therefore substantiallyincreased.

[0005] The present invention comprises an improved geomembrane andmethod of manufacture which overcomes the foregoing and otherdifficulties which have long since characterized the prior art. Moreparticularly, the present invention comprises an improved geomembraneconstruction which is directly bondable to a geosynthetic clay liner tocomplete the construction of a liner for landfills, canals, ponds, andsimilar constructions. In accordance with the preferred embodiment ofthe invention, the geomembrane comprises a unitary structure includingan adhesive layer and a barrier layer which are fabricated byco-extrusion. The geomembrane of the present invention may furtherinclude a third co-extruded layer which may be textured.

[0006] By means of the present invention the fabrication of liners forearthen constructions such as landfills, canals, ponds, and the like isgreatly simplified. The improved geomembrane of the present invention isdirectly bondable to a geosynthetic clay liner to complete theconstruction of the liner, thereby eliminating the necessity of aseparate adhesive application step. The use of the invention alsoresults in an improved liner construction wherein the possibility ofseparation of the geomembrane from the remaining components of the lineris substantially eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] A more complete understanding of the invention may be gained byreference to the following Detailed Description when presented inconjunction with the accompanying Drawings, wherein:

[0008]FIG. 1 is a diagrammatic illustration of the installation of aliner in a landfill, canal, pond, or similar earthen construction;

[0009]FIG. 2 is a sectional view illustrating a liner for landfills,canals, ponds, and similar construction incorporating the geomembrane ofthe present invention;

[0010]FIG. 3 is an exploded view of the liner of FIG. 2 furtherillustrating the invention;

[0011]FIG. 4 is a sectional view illustrating a first embodiment of themethod of the present invention; and

[0012]FIG. 5 is a sectional view illustrating a second embodiment of themethod of the present invention.

DETAILED DESCRIPTION

[0013] Referring now to the Drawings, and particularly to FIG. 1thereof, the use of a liner incorporating the geomembrane of the presentinvention is diagrammatically illustrated. An excavation 10 is formed inthe earth. The excavation 10 may ultimately comprise a landfill, acanal, a pond, or similar earthen construction. A trench 12 is formedalong the sides of the excavation 10, it being understood that theconfiguration of the trench 12 depends upon the configuration of theexcavation 10. A liner 14 incorporating the geomembrane of the presentinvention is provided in rolls. The liner 14 is unrolled in overlappingstrips utilizing an appropriate vehicle 16. Each end of each stripcomprising the liner 14 extends into the trench 12. Followinginstallation of the liner 14, backfill 18 is installed in trench 12 tosecure the liner in place.

[0014] Referring to FIG. 2, liner 14 includes a geosynthetic clay liner20 and a geomembrane 22 comprising the present invention. Thegeosynthetic clay liner 20 comprises a clay layer 24 which may comprisebentonite. The clay layer 24 is retained by a layer of wovenpolypropylene fabric 26 extending across the upper surface thereof. Alayer of non-woven polypropylene material 28 extends across the lowersurface of the clay layer 24.

[0015] The geomembrane 22 of the liner 14 is further illustrated in FIG.3. The geomembrane 22 comprises a two layer construction, including athermoplastic adhesive layer 30 and a barrier layer 32. The geomembrane22 may also include a third layer 34, which may be textured as shown. Inaccordance with the invention, the geomembrane 22 comprises a unitarystructure fabricated by co-extrusion.

[0016] The adhesive layer 30 of the geomembrane 22 may be formed fromany of the following materials:

[0017] Ethylene Vinyl Acetate(EVA)

[0018] Ionomer

[0019] Ethylene Methyl Acrylate(EMA)

[0020] Ethylene Acrylic Acid(EAA)

[0021] Ethylene Methyl Acrylic Acid(EMAA)

[0022] Ethylene Ethyl Acrylate(EEA)

[0023] Polyethylene with density below 0.915 gm/cc

[0024] Polyolefins, copolymers and terpolymers of polyolefins with meltpoints below the melt point of the barrier layer 32.

[0025] The barrier layer 32 and the third layer 34, if used, may beformed from any of the following materials:

[0026] High Density Polyethylene

[0027] Linear Low Density Polyethylene

[0028] Low Density Polyethylene

[0029] Ultra Low Density Polyethylene

[0030] Very Low Density Polyethylene

[0031] Polypropylene

[0032] Polypropylene copolymers and terpolymers

[0033] Polyethylene with natural density between 0.880 and 0.950 gm/cc.

[0034] Any of the following techniques may be used to provide a texturedsurface on the third layer, if desired:

[0035] Use of chemical blowing agents

[0036] Use of compressed gas blowing agents including nitrogen

[0037] Use of post extrusion texturing process such as lamination,spray-on, or embossing.

[0038]FIG. 4 illustrates a first embodiment of the method of the presentinvention. A conventional co-extrusion die 36, of the type used to makecast co-extrusions, receives a molten thermoplastic adhesive which willeventually form the adhesive layer of the geomembrane 22 through aninlet 38. Molten thermoplastic material which eventually will form thebarrier layer 32 of the geomembrane 22, is received through inlet 40. Ifthe geomembrane 22 is to include a third layer, molten thermoplasticmaterial which eventually will form the layer 34 of the geomembrane 22,is received through inlet 42. The materials received through the inletsof the die 36 are directed through a combining adapter 44 and areco-extruded to form the geomembrane 22 of the present invention.

[0039]FIG. 5 illustrates a second embodiment of the method of thepresent invention. A blown film co-extrusion die 46 receives moltenthermoplastic adhesive material which eventually will comprise theadhesive layer 30 of the geomembrane 22 through a cylindrical inlet 48.Molten thermoplastic material, which eventually will form the core 32 ofthe geomembrane 22, is received through a cylindrical inlet 50. If thegeomembrane is to include a third layer, molten thermoplastic material,which eventually will form the layer 34 of the geomembrane 22, isreceived through inlet 52. Within the die 46, the materials receivedthrough the inlets are co-extruded to form a blown film comprising thegeomembrane 22 of the present invention.

[0040] Referring again to FIG. 2, the geomembrane of the presentinvention is hot as it leaves the die 36 or the die 46. Therefore,immediately following the manufacture thereof, the geomembrane 22 may besecured to the outer surface of the non-woven polypropylene textilelayer 28 comprising the geosynthetic clay liner 20. The adhesive layer30 of the geomembrane 22 adhesively secures the geomembrane 22 to thenon-woven polypropylene material layer 28 thereby securely joining thegeomembrane 22 of the present invention to the geosynthetic clay liner20. The use of the adhesive layer 30 to secure the geomembrane 22 to thegeosynthetic clay liner 20 assures complete bonding between thegeomembrane 22 and the geosynthetic clay liner 20 thereby preventingseparation during use.

[0041] Alternatively, the geomembrane 22 may be cooled following itsmanufacture. The geomembrane is then formed into rolls for transport toa separate assembly location. The geomembrane is unrolled and theadhesive layer thereof is heated to facilitate bonding of thegeomembrane 22 to the geosynthetic clay liner 20.

[0042] Although preferred embodiments of the invention have beenillustrated in the accompanying Drawings and described in the foregoingDetailed Description, it will be understood that the invention is notlimited to the embodiments disclosed, but is capable of numerousrearrangements, modifications, and substitutions of parts and elementswithout departing from the spirit of the invention.

The claims
 1. For use in the manufacture of liners for earthenconstructions, a geomembrane comprising a unitary construction formed byco-extrusion and including a thermoplastic barrier layer and athermoplastic adhesive layer secured on one side of the barrier layer.2. The geomembrane according to claim 1 wherein the adhesive layer isformed from a material selected from the group including: ethylene vinylacetate (EVA) ionomer ethylene methyl acrylate (EMA) ethylene acrylicacid (EAA) ethylene ethyl acrylate (EEA) and ethylene methyl acrylicacid (EMAA).
 3. The geomembrane according to claim 1 wherein theadhesive layer is formed from polyethylene having a density less than0.915 gm/cc.
 4. The geomembrane according to claim 1 wherein theadhesive layer is formed from a material selected from the groupincluding polyolefins, copolymers of polyolefins, and terpolymers ofpolyolefins, said material having a melting point below that of thebarrier layer.
 5. The geomembrane according to claim 1 wherein thethermoplastic barrier layer is formed from a material selected from thegroup including: high density polyethylene linear low densitypolyethylene low density polyethylene ultra low density polyethylene p1very low density polyethylene polypropylene copolymers of polypropylene,and terpolymers of polypropylene.
 6. The geomembrane according to claim1 wherein the barrier layer is formed from polyethylene having a naturaldensity of between about 0.880 and about 0.950 gm/cc.
 7. The geomembraneaccording to claim 1 wherein the barrier layer comprises high densitypolyethylene and the thermoplastic adhesive layer comprisesethylene-vinyl acetate.
 8. For use in the manufacture of liners forearthen constructions, a geomembrane comprising a unitary constructionformed by co-extrusion and including a thermoplastic barrier layer, athermoplastic adhesive layer secured on one side of the barrier layer,and a third thermoplastic layer secured on the opposite side of thebarrier layer.
 9. The geomembrane according to claim 8 wherein theadhesive layer is formed from a material selected from the groupincluding: ethylene vinyl acetate (EVA) ionomer ethylene methyl acrylate(EMA) ethylene acrylic acid (EAA) ethylene ethyl acrylate (EEA) andethylene methyl acrylic acid (EMAA).
 10. The geomembrane according toclaim 8 wherein the adhesive layer is formed from polyethylene having adensity less than 0.915 gm/cc.
 11. The geomembrane according to claim 8wherein the adhesive layer is formed from a material selected from thegroup including polyolefins, copolymers of polyolefins, and terpolymersof polyolefins, said material having a melting point below that of thebarrier layer.
 12. The geomembrane according to claim 8 wherein thethermoplastic barrier layer is formed from a material selected from thegroup including: high density polyethylene linear low densitypolyethylene low density polyethylene ultra low density polyethylenevery low density polyethylene polypropylene copolymers of polypropylene,and terpolymers of polypropylene.
 13. The geomembrane according to claim6 wherein the barrier layer is formed from polyethylene having a naturaldensity of between about 0.880 and about 0.950 gm/cc.
 14. Thegeomembrane according to claim 8 wherein the thermoplastic third layeris formed from a material selected from the group including: highdensity polyethylene linear low density polyethylene low densitypolyethylene ultra low density polyethylene very low densitypolyethylene polypropylene copolymers of polypropylene, and terpolymersof polypropylene.
 15. The geomembrane according to claim 8 wherein thethird layer is formed from polyethylene having a natural density ofbetween about 0.880 and about 0.950 gm/cc.
 16. The geomembrane accordingto claim 5 wherein the third thermoplastic layer comprises athermoplastic material initially having a blowing agent therein which isreleased following co-extrusion of the geomembrane to form a texturedsurface thereof.
 17. The geomembrane according to claim 5 wherein thebarrier layer comprises high density polyethylene, the thermoplasticadhesive layer comprises ethylene-vinyl acetate, and the thirdthermoplastic layer comprises high density polyethylene initially havinga blowing agent mixed therein which is released following theco-extrusion of the geomembrane to form the textured surface.
 18. Amethod of fabricating a geomembrane for use in manufacturing liners forearthen constructions including the steps of: providing a quantity ofthermoplastic material; providing a quantity of thermoplastic adhesivematerial; co-extruding the quantity of thermoplastic material and thequantity of thermoplastic adhesive material to form a unitaryconstruction comprising a barrier layer formed from the thermoplasticmaterial and an adhesive layer formed from the thermoplastic adhesivematerial secured to one side of the barrier layer.
 19. The methodaccording to claim 18 wherein the step of providing a quantity ofthermoplastic material is carried out by providing a quantity of amaterial selected from the group including: high density polyethylenelinear low density polyethylene low density polyethylene ultra lowdensity polyethylene very low density polyethylene polypropylenecopolymers of polypropylene, and terpolymers of polypropylene.
 20. Themethod according to claim 18 wherein the step of providing a quantity ofa thermoplastic adhesive material is carried out by providing a quantityof a material selected from the group including: ethylene vinyl acetate(EVA) ionomer ethylene methyl acrylate (EMA) ethylene acrylic acid (EAA)ethylene ethyl acrylate (EEA) and ethylene methyl acrylic acid (EMAA).21. The method according to claim 18 wherein the step of providing aquantity of thermoplastic material is carried out by providing aquantity of high density polyethylene and wherein the step of providinga quantity of thermoplastic adhesive material is carried out byproviding a quantity of ethylene-vinyl acetate.
 22. A method offabricating a geomembrane for use in manufacturing liners for earthenconstructions including the steps of: providing a first quantity ofthermoplastic material; providing a quantity of thermoplastic adhesivematerial; providing a second quantity of thermoplastic material having ablowing agent mixed therein; co-extruding the first quantity ofthermoplastic material, the quantity of thermoplastic adhesive material,and the quantity thermoplastic material to form a unitary constructioncomprising a barrier formed from the first quantity thermoplasticmaterial, an adhesive layer formed from the thermoplastic adhesivematerial secured to one side of the center core and a layer formed fromthe second quantity of thermoplastic material adhesively secured to theopposite side of the center core.
 23. The method according to claim 22wherein the step of providing a first quantity of thermoplastic materialis carried out by providing a quantity of a material selected from thegroup including: high density polyethylene linear low densitypolyethylene low density polyethylene ultra low density polyethylenevery low density polyethylene polypropylene copolymers of polypropylene,and terpolymers of polypropylene.
 24. The method according to claim 22wherein the step of providing a quantity of a thermoplastic adhesivematerial is carried out by providing a material selected from the groupincluding: ethylene vinyl acetate (EVA) ionomer ethylene methyl acrylate(EMA) ethylene acrylic acid (EAA) ethylene ethyl acrylate (EEA) andethylene methyl acrylic acid (EMAA).
 25. The method according to claim22 wherein the step of providing a second quantity of thermoplasticmaterial is carried out by providing a quantity of a material selectedfrom the group including: high density polyethylene linear low densitypolyethylene low density polyethylene ultra low density polyethylenevery low density polyethylene polypropylene copolymers of polypropylene,and terpolymers of polypropylene.
 26. The method according to claim 22wherein the step of providing a first quantity of thermoplastic materialis carried out by providing a quantity of high density polyethylene,wherein the step of providing a quantity of thermoplastic adhesivematerial is carried out by providing a quantity of ethylene-vinylacetate, and wherein the step of providing a second quantity ofthermoplastic material is carried out by providing a quantity of highdensity polyethylene having a blowing agent mixed therein.
 27. A linerfor earthen constructions comprising: a. a geosynthetic clay linerincluding a clay layer, a first layer of geotextile extending across oneside of the clay layer, and a second layer of geotextile extendingacross the other side of the clay layer; b. a geomembrane comprising aunitary construction formed by co-extrusion and including athermoplastic barrier core layer, a thermoplastic adhesive layer securedon one side of the barrier layer, and a textured thermoplastic layersecured on the opposite side of the barrier layer; the layer ofthermoplastic adhesive material comprising the geomembrane beingadhesively secured to the second layer of geotextile comprising thegeosynthetic clay liner.
 28. The liner according to claim 27 wherein thebarrier layer of the geomembrane is formed from a material selected fromthe group including: high density polyethylene linear low densitypolyethylene low density polyethylene ultra low density polyethylenevery low density polyethylene polypropylene copolymers of polypropylene,and terpolymers of polypropylene.
 29. The liner according to claim 27wherein the thermoplastic adhesive layer of the geomembrane is formedfrom a material selected from the group including: ethylene vinylacetate (EVA) ionomer ethylene methyl acrylate (EMA) ethylene acrylicacid (EAA) ethylene ethyl acrylate (EEA) and ethylene methyl acrylicacid (EMAA).
 30. The liner according to claim 27 wherein the texturedthermoplastic layer of the geomembrane comprises a thermoplasticmaterial initially having a blowing agent mixed therein which isreleased following co-extrusion of the geomembrane to form the texturedsurface thereof.
 31. The liner according to claim 27 wherein the barrierlayer of the geomembrane comprises high density polyethylene, thethermoplastic layer comprises ethylene-vinyl acetate, and the texturedlayer of the geomembrane comprises high density polyethylene initiallyhaving a blowing agent mixed therein which is released following theco-extrusion of the geomembrane to form the textured surface.